Camera, accessory apparatus, communication control method, storage medium, and camera system

ABSTRACT

A camera includes a lens-camera communication controller and an adapter-camera communication controller. The camera-lens communication channel includes a first data communication channel used during a data communication and a first notification channel used for a notification of a timing of a communication via the first data communication channel. The camera-adapter communication channel includes a second data communication channel used during the data communication and a second notification channel used for a notification of a timing of a communication via the second data communication channel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of International Patent ApplicationNo. PCT/JP2018/020729, filed on May 30, 2018, which claims the benefitof Japanese Patent Application Nos. 2017-107342, filed on May 31, 2017,and 2018-102895, filed on May 30, 2018, which are hereby incorporated byreference herein in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a camera system including a camera andan accessory apparatus, such as an interchangeable lens or an adapter,which can communicate with each other.

Description of the Related Art

In an interchangeable lens type camera system including a camera towhich an interchangeable lens is detachably attachable, a communicationis performed for the camera to control the operation of theinterchangeable lens and for the interchangeable lens to provide thecamera with data necessary for its control and imaging. In particular,in imaging a recording use motion image and a live-view display usemotion image with the interchangeable lens, a smooth lens control isrequired at an imaging cycle, so it is necessary to synchronize theimaging timing of the camera and the control timing of theinterchangeable lens with each other. Thus, the camera needs to completea data reception from the interchangeable lens and a transmission of acommand, such as a variety of instructions and requests, to theinterchangeable lens within the imaging cycle. However, as a data amountreceived by the camera from the interchangeable lens becomes larger orthe imaging cycle becomes shorter (or the frame rate becomes higher), acommunication of a large amount of data at higher speed is required.

An adapter such as a wide converter or a teleconverter (extender) may beconnected between the camera and the interchangeable lens, and this typeof adapter also communicates with the camera similar to theinterchangeable lens. Hence, the camera system requires a communicationsystem in which the camera can perform a one-to-many communication witha plurality of accessory apparatuses including the interchangeable lensand the adapter. As a communication method for realizing the one-to-manycommunication between a communication master and a plurality ofcommunication slaves, there is an I²C communication method disclosed inNXP materials: I²C bus specification and user manual Rev5.0J-2-Oct. 9,2012 [May 20, 2017 Internet search URL:http://www.nxp.com/documents/user_manual/UM10204_JA.pdf].

However, the address of the communication slave that can be specified bythe I²C bus is fixed for each communication slave or selected by theuser from a slight width (about several bits) by hardware. In any ofthese cases, the communication master needs to previously recognize theaddresses of a plurality of communication slaves connected to it.

On the other hand, in a camera system that can connect in series aplurality of accessory apparatuses as the communication slaves, thecamera as the communication master may not previously know what types ofaccessory apparatuses and how many accessory apparatuses (such as newlyused ones) are connected. In this case, assume that addresses of 0 to nare assignable to the communication slaves. A camera that does not knowtype(s) and number of connected accessory apparatuses needs to performan authentication communication to authenticate (confirm) the accessoryapparatus for all addresses from 0 to n including an address where noaccessory apparatus exists. As a result, it takes a long time for theauthentication communication, and the start of imaging by the camerasystem is delayed.

SUMMARY OF THE INVENTION

The present invention provides a camera, an accessory apparatus, acommunication control method, a storage medium, and a camera system,each of which can permit the camera to which a plurality of accessoryapparatuses are connected to perform an authentication communicationwith all the accessory apparatuses in a short time.

A camera according to one aspect of the present invention usable while aplurality of accessory apparatuses are connected to the camera, thecamera comprising a camera controller configured to control acommunication with the plurality of accessory apparatuses using a signaltransmission channel used for a signal transmission between the cameraand the plurality of accessory apparatuses, and a data communicationchannel used for a data communication between the camera and theplurality of accessory apparatuses. Using the data communicationchannel, the camera controller is configured to provide a firstcommunication that is a data communication with the plurality ofaccessory apparatuses and a second communication that is an individualdata communication with a specific accessory apparatus among theplurality of accessory apparatuses, wherein whenever detecting a signalindicating an ongoing standby of the first communication output to thesignal transmission channel from one accessory apparatus that is notauthenticated by the camera among the plurality of accessoryapparatuses, the camera controller sequentially authenticates each ofthe plurality of accessory apparatuses by performing an authenticationcommunication with the one accessory apparatus.

An accessory apparatus according to another aspect of the presentinvention among a plurality of accessory apparatuses connectable to acamera usable while the plurality of accessory apparatuses are connectedto the camera, the accessory apparatus comprising an accessorycontroller configured to control a communication with the camera using asignal transmission channel used for a signal transmission between thecamera and the plurality of accessory apparatuses, and a datacommunication channel used for a data communication between the cameraand the plurality of accessory apparatuses. The accessory controller isconfigured to provide a first communication that is a data communicationincluding a reception of data sent from the camera to the plurality ofaccessory apparatuses and a second communication that is an individualdata communication with the camera, using the data communicationchannel, outputs a signal indicating the accessory controller is waitingfor the first communication to the signal transmission channel when theaccessory controller is not authenticated by the camera, and performs anauthentication communication for causing the camera that has detectedthe output to authenticate the accessory apparatus.

A communication control method according to another aspect of thepresent invention is for a camera usable while a plurality of accessoryapparatuses are connected to the camera, and connected to a signaltransmission channel used to a signal transmission between the cameraand the plurality of accessory apparatuses, and a data communicationchannel used for a data communication between the camera and theplurality of accessory apparatuses. The camera being configured toprovide a first communication that is a data communication with theplurality of accessory apparatuses and a second communication that is anindividual data communication with a specific accessory apparatus amongthe plurality of accessory apparatuses, using the data communicationchannel. The communication control method includes the steps of causingthe camera to detect a signal indicating an ongoing standby of the firstcommunication output to the signal transmission channel from oneaccessory apparatus that is not authenticated by the camera among theplurality of accessory apparatuses, and causing the camera to perform anauthentication communication with the one accessory apparatus, whereinwhenever detecting the signal indicating the ongoing standby, the camerasequentially authenticates each of the plurality of accessoryapparatuses by performing the authentication communication with the oneaccessory apparatus.

A communication control method according to another aspect of thepresent invention is for an accessory apparatus among a plurality ofaccessory apparatuses connectable to a camera usable while the pluralityof accessory apparatuses are connected to the camera, the accessoryapparatus being connected to a signal transmission channel used for asignal transmission between the camera and the plurality of accessoryapparatuses, and a data communication channel used for a datacommunication between the camera and the plurality of accessoryapparatuses. The accessory apparatus is configured to provide a firstcommunication that is a data communication including a reception of datasent from the camera to the plurality of accessory apparatuses and asecond communication that is an individual data communication with thecamera, using the data communication channel. The communication controlmethod includes the steps of causing the accessory apparatus to output asignal indicating the accessory controller is waiting for the firstcommunication to the signal transmission channel when the accessorycontroller is not authenticated by the camera, and causing the accessoryapparatus to perform an authentication communication for causing thecamera that has detected the output to authenticate the accessoryapparatus.

A communication control program that is a computer program that causes acomputer in a camera or an accessory apparatus to execute the abovecommunication control method also constitutes another aspect of thepresent invention.

A camera system according to another aspect of the present inventionincludes a plurality of accessory apparatuses, and a camera usable whilethe plurality of accessory apparatuses are connected to the camera.Using a data communication channel used for a data communication betweenthe camera and the plurality of accessory apparatuses, the cameraincludes a camera controller configured to provide a first communicationthat is a data communication with the plurality of accessory apparatusesand a second communication that is an individual data communication witha specific accessory apparatus among the plurality of accessoryapparatuses. Each of the plurality of accessory apparatuses includes anaccessory controller configured to provide the first communication andthe second communication with the camera controller. The accessorycontroller in one accessory apparatus among the plurality of accessoryapparatus which is not authenticated by the camera outputs a signalindicating an ongoing standby of the first communication to the signaltransmission channel, wherein whenever detecting the signal indicatingthe ongoing standby, the camera controller sequentially authenticateseach of the plurality of accessory apparatuses by performing anauthentication communication with the one accessory apparatus.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a configuration of a camera systemaccording to a first embodiment of the present invention.

FIG. 2 is a diagram showing communication circuits of a camera (cameramicrocomputer), an interchangeable lens (lens microcomputer), and anadapter (adapter microcomputer) according to the first embodiment.

FIG. 3 is a diagram showing a communication format according to thefirst embodiment.

FIG. 4 is a diagram showing communication waveforms in a broadcastcommunication according to the first embodiment.

FIG. 5 is a diagram showing communication waveforms in a P2Pcommunication according to the first embodiment.

FIG. 6 is a diagram showing communication waveforms when thecommunication mode is switched in the first embodiment.

FIG. 7A is a flowchart illustrating processing of the camera in thebroadcast communication according to the first embodiment.

FIG. 7B is a flowchart showing processing of the interchangeable lensand the adapter in the broadcast communication according to the firstembodiment.

FIG. 8A is a flowchart illustrating processing of the camera in the P2Pcommunication according to the first embodiment.

FIG. 8B is a flowchart illustrating processing of the interchangeablelens and the adapter in the P2P communication according to the firstembodiment.

FIG. 9 is a diagram showing communication waveforms in authenticationcommunication processing according to the first embodiment.

FIG. 10 is a flowchart showing authentication communication processingaccording to the first embodiment.

FIG. 11 is a diagram showing communication circuits of a camera (cameramicrocomputer), an interchangeable lens (lens microcomputer), and anadapter (adapter microcomputer) according to a second embodiment of thepresent invention.

FIG. 12 is a diagram showing communication waveforms in authenticationcommunication processing according to the second embodiment.

FIG. 13 is a flowchart illustrating authentication communicationprocessing according to the second embodiment.

FIG. 14 is a diagram illustrating other communication channels.

DESCRIPTION OF THE EMBODIMENTS

Referring now to the accompanying drawings, a description will be givenof embodiments according to the present invention.

First Embodiment

FIG. 1 illustrates a configuration of a camera system according to afirst embodiment of the present invention that includes a camera 200,and an interchangeable lens 100 and an intermediate adapter apparatus(simply referred to as an adapter hereinafter) 300 as accessoryapparatuses. This embodiment illustrates the camera 200 usable while theinterchangeable lens 100 is connected via the adapter 300 (while aplurality of accessory apparatuses are connected).

While FIG. 1 illustrates an illustrative camera system in which a singleadapter 300 is connected between the camera 200 and the interchangeablelens 100, a plurality of adapters may be connected in series between thecamera 200 and the interchangeable lens 100.

The camera system according to this embodiment performs communicationsamong the camera 200, the interchangeable lens 100, and the adapter 300using a plurality of communication methods. The camera 200, theinterchangeable lens 100, and the adapter 300 transmit control commandsand data (information) through their respective communicators. Inaddition, each communicator supports a plurality of communicationmethods, and can select an optimal communication method in a variety ofsituations by switching to the common communication method insynchronization with each other according to the type of data to becommunicated and the purpose of communication.

A description will now be given of a more specific configuration of theinterchangeable lens 100, the camera 200, and the adapter 300.

The interchangeable lens 100 and the adapter 300 are mechanically andelectrically connected via a mount 400 as a coupling mechanism.Similarly, the adapter 300 and the camera 200 are mechanically andelectrically connected via a mount 401 as a coupling mechanism. Theinterchangeable lens 100 and the adapter 300 obtain the electric powerfrom the camera 200 through power supply terminal portions (not shown)provided to the mounts 400 and 401. Then, the power is suppled which isnecessary for operations of a variety of actuators, a lens microcomputer111, and an adapter microcomputer 302 as described later. Theinterchangeable lens 100, the camera 200, and the adapter 300communicate with each other through communication terminal portions(illustrated in FIG. 2 ) provided to the mounts 400 and 401.

The interchangeable lens 100 includes an imaging optical system. Theimaging optical system includes, in order from an object OBJ side, afield lens 101, a magnification varying lens 102 that changes amagnification, a diaphragm unit 114 that adjusts a light amount. Theimaging optical system further includes an image stabilization lens 103configured to reduce (correct) an image blur, and a focus lens 104 usedfor focusing.

The zoom lens 102 and the focus lens 104 are held by lens holding frames105 and 106, respectively. The lens holding frames 105 and 106 aremovably guided in an optical axis direction (indicated by a broken linein the figure) by unillustrated guide shafts, and are driven in theoptical axis direction by stepping motors 107 and 108. The steppingmotors 107 and 108 move the zoom lens 102 and the focus lens 104 insynchronization with a driving pulse, respectively.

The image stabilization lens 103 shifts in a direction orthogonal to theoptical axis in the imaging optical system to reduce image blurs causedby a camera shake such as a manual shake.

A lens microcomputer 111 serves as a lens controller (accessorycontroller) that controls the operation of each component in theinterchangeable lens 100. The lens microcomputer 111 receives a controlcommand and a transmission request command transmitted from the camera200 via a lens communicator (accessory communicator) 112 including alens communication interface circuit. The lens microcomputer 111performs a lens control corresponding to the control command, andtransmits lens data corresponding to the transmission request command tothe camera 200 via the lens communicator 112.

The lens microcomputer 111 outputs a driving signal to a zoom drivingcircuit 119 and a focus driving circuit 120 in response to a commandrelating to a magnification variation and focusing among the controlcommands to drive the stepping motors 107 and 108. This configurationcan provide zoom processing for controlling the magnification varyingoperation with the zoom lens 102 and AF (autofocus) processing forcontrolling the focusing operation with the focus lens 104.

The diaphragm unit 114 includes aperture blades 114 a and 114 b. Thestates (positions) of the aperture blades 114 a and 114 b are detectedby a Hall element 115. The output from the Hall element 115 is input tothe lens microcomputer 111 via an amplifier circuit 122 and an A/Dconversion circuit 123. The lens microcomputer 111 outputs a drivingsignal to a diaphragm driving circuit 121 based on an input signal fromthe A/D conversion circuit 123 to drive a diaphragm actuator 113.Thereby, a light amount adjustment operation by the diaphragm unit 114is controlled.

The lens microcomputer 111 controls an image stabilization actuator(voice coil motor etc.) 126 via an image stabilization driving circuit125 in accordance with the camera shake detected by a shake sensor (notshown) such as a vibration gyro provided in the interchangeable lens100. Thereby, the image stabilization processing for controlling theshift operation (image stabilization operation) of the imagestabilization lens 103 is performed.

The interchangeable lens 100 includes a manual operation ring (simplyreferred to as an operation ring hereinafter) 130 and an operation ringdetector 131. The operation ring detector 131 includes, for example, twophoto-interrupters that output two-phase signals in accordance with arotation of the operation ring 130. The lens microcomputer 111 candetect the rotational operation amount of the operation ring 130. Thelens microcomputer 111 can notify the camera microcomputer 205 of therotational operation amount of the operation ring 130 via the lenscommunicator 112.

The adapter 300 includes, for example, an extender for changing a focallength, and includes a magnification varying lens 301 and an adaptermicrocomputer 302. The adapter microcomputer 302 is an adaptercontroller (accessory controller) that controls the operation of eachcomponent in the adapter 300. The adapter microcomputer 302 receives acontrol command and a transmission request command transmitted from thecamera 200 via an adapter communicator (accessory communicator) 303including a communication interface circuit. The adapter microcomputer302 performs an adapter control corresponding to the control command,and transmits adapter data corresponding to the transmission requestcommand to the camera 200 via the adapter communicator 303.

The camera 200 includes an image sensor 201, such as a CCD sensor or aCMOS sensor, an A/D conversion circuit 202, a signal processing circuit203, a recorder 204, a camera microcomputer 205, and a display unit 206.

The image sensor 201 photoelectrically converts an object image formedby the imaging optical system in the interchangeable lens 100 andoutputs an electrical signal (analog signal). The A/D conversion circuit202 converts the analog signal from the image sensor 201 into a digitalsignal. The signal processing circuit 203 performs various types ofimage processing for the digital signal from the A/D conversion circuit202 and generates an image signal. The signal processing circuit 203also generates, from the image signal, focus information indicating acontrast state of an object image (focus state of the imaging opticalsystem) and luminance information indicating an exposure state. Thesignal processing circuit 203 outputs the image signal to the displayunit 206, and the display unit 206 displays the image signal as alive-view image used for a confirmation of a composition, a focus state,etc.

A camera microcomputer 205 as a camera controller controls the camera200 in accordance with an input from a camera operation member, such asan unillustrated imaging instructing switch and a variety of settingswitches. The camera microcomputer 205 transmits a control commandrelating to the magnification varying operation of the zoom lens 102 tothe lens microcomputer 111 in accordance with the operation of anunillustrated zoom switch via the camera communicator 208 including thecommunication interface circuit. Moreover, the camera microcomputer 205transmits, to the lens microcomputer 111 via the camera communicator208, a control command relating to the light amount adjustment operationof the diaphragm unit 114 in accordance with the luminance informationand the focusing operation of the focus lens 104 in accordance with thefocus information. The camera microcomputer 205 transmits a transmissionrequest command for acquiring the control information and statusinformation of the interchangeable lens 100 to the lens microcomputer111, if necessary. Further, the camera microcomputer 205 transmits tothe adapter microcomputer 302 a transmission request command foracquiring the control information and status information of the adapter300.

Referring now to FIG. 2 , a description will be given of a communicationcircuit configured among the camera 200 (camera microcomputer 205), theinterchangeable lens 100 (lens microcomputer 111), and the adapter 300(adapter microcomputer 302). The camera microcomputer 205, the lensmicrocomputer 111, and the adapter microcomputer 302 achievecommunications using signal lines connected via communication terminalportions provided on the mounts 400 and 401.

The signal lines include a signal line (first signal line correspondingto a signal transmission channel) CS that communicates a signal for acommunication control, and a signal line (second signal corresponding toa data communication channel) DATA for a data communication.

The signal line CS is connected to the camera microcomputer 205, theadapter microcomputer 302, and the lens microcomputer 111. Therefore,the camera microcomputer 205, the adapter microcomputer 302, and thelens microcomputer 111 can detect high and low levels of the state ofthe signal line CS. The signal line CS is pulled up to an unillustratedpower source in the camera 200. The signal line CS can be connected to aground GND (open drain connection) via a ground switch 1121 in theinterchangeable lens 100, a ground switch 2081 in the camera 200, and aground switch 3031 in the adapter 300.

Due to this configuration, the camera microcomputer 205, the adaptermicrocomputer 302, and the lens microcomputer 111 can put the signalline CS into low by turning on (connecting) the ground switches 2081,1121, and 3031, respectively. In addition, the camera microcomputer 205,the adapter microcomputer 302, and the lens microcomputer 111 can putthe signal line CS into high by turning off (disconnect) the groundswitches 2081, 1121, and 3031, respectively.

Furthermore, a CS switch (channel switch) 3033 is provided in theadapter 300. The adapter microcomputer 302 can connect and disconnectthe signal line CS by switching the CS switch 3033 between the connectedstate and the disconnected state. In the disconnected state of the CSswitch 3033, the signal output state from the camera side (camera 200 inthis embodiment) of the adapter 300 to the signal line CS and the signaloutput state from the adapter 300 to the signal line CS are nottransmitted to the interchangeable lens side (interchangeable lens 100in this embodiment). In other words, the broadcast communicationdescribed later is unavailable from the adapter 300 to the communicationslave on the interchangeable lens side. A detailed description will begiven later of a communication control signal (instruction ornotification) transmitted through the signal line CS and its outputprocessing.

The signal line DATA is a single-wire bidirectional data communicationline that can be used by switching the data transmission direction. Thesignal line DATA is connectable to the lens microcomputer 111 via aninput/output switch 1122 in the interchangeable lens 100, andconnectable to the camera microcomputer 205 via an input/output switch2082 in the camera 200. The signal line DATA is connectable to theadapter microcomputer 302 via an input/output switch 3032 in the adapter300. Each microcomputer includes a CMOS type data output part fortransmitting data and a CMOS type data input part for receiving data(none of which is shown). Each microcomputer can select whether thesignal line DATA is connected to the data output part or the data inputpart, by switching the input/output switch.

Each of the camera microcomputer 205, the adapter microcomputer 302, andthe lens microcomputer 111 when transmitting data sets the input/outputswitch so as to connect the signal line DATA to the data output part.Each of the camera microcomputer 205, the adapter microcomputer 302, andthe lens microcomputer 111 when receiving data sets an input/outputswitch so as to connect the signal line DATA to the data input part.Details of the input/output switching processing of the signal line DATAwill be described later.

FIG. 2 illustrates an illustrative communication circuit, but anothercommunication circuit may be used. For example, the signal line CS maybe pulled down to GND in the camera 200 and connected to anunillustrated power supply via the ground switch 1121 in theinterchangeable lens 100, the ground switch 2081 in the camera 200, andthe ground switch 3031 in the adapter 300. In the interchangeable lens100, the camera 200, and the adapter 300, the signal line DATA may bealways connected to the data input part, and the connection anddisconnection between the signal line DATA and the data output part maybe selected by a switch.

[Communication Data Format]

Referring now to FIG. 3 , a description will be given of a format ofcommunication data exchanged among the camera 200 (camera microcomputer205), the interchangeable lens 100 (lens microcomputer 111), and theadapter 300 (adapter microcomputer 302). This communication data formatis common to the broadcast communication, which is a first communicationdescribed later, and the P2P communication, which is a secondcommunication. A description will now be given of a communication dataformat in a so-called asynchronous communication in which acommunication speed used for a communication among the microcomputersare previously determined and the transmission and reception areperformed at a communication bit rate in accordance with the protocol.

Initially, in a non-transmission state that transmits no data, thesignal level is maintained high. Next, in order to notify the datareception side of a start of the data transmission, the signal level isset to be low for one bit period. This one bit period will be referredto as a start bit ST. Next, one-byte data is transmitted for aneight-bit period from the next second bit to the ninth bit. The bitarrangement of the data starts with the most significant data D7 in theMSB first format, continues with data D6, data D5, . . . , Data D1, andends with the least significant data D0. In the tenth bit, one-bitparity PA information is added, and one frame level starting from thestart bit ST is completed by finally putting the signal level into highduring a stop bit SP period indicating the end of the transmission data.

FIG. 3 illustrates an illustrative communication data format, butanother communication data format may be used. For example, the bitarrangement of the data may be the LSB first or the nine-bit length, orno parity PA information need not be added. The communication dataformat may be switched between broadcast communication and the P2Pcommunication.

[Broadcast Communication]

Next follows a description of the broadcast communication (firstcommunication). The broadcast communication is the one-to-manycommunication in which one of the camera microcomputer 205, the lensmicrocomputer 111, and the adapter microcomputer 302 transmits data tothe other two at the same time (i.e., simultaneous transmission). Thisbroadcast communication is performed using the signal line CS and thesignal line DATA. A communication mode in which the broadcastcommunication is performed is also referred to as a broadcastcommunication mode (first communication mode).

FIG. 4 illustrates signal waveforms in the broadcast communication amongthe camera microcomputer 205, the lens microcomputer 111, and theadapter microcomputer 302. Here is an example in which the adaptermicrocomputer 302 performs the broadcast communication to the cameramicrocomputer 205 and the lens microcomputer 111 in response to thebroadcast communication from the camera microcomputer 205 to the lensmicrocomputer 111 and the adapter microcomputer 302.

Initially, the camera microcomputer 205 as a communication master startsthe low output to the signal line CS in order to notify the lensmicrocomputer 111 and the adapter microcomputer 302 as communicationslaves that the broadcast communication is to be started. Next, thecamera microcomputer 205 outputs data to be transmitted, to the signalline DATA. On the other hand, the lens microcomputer 111 and the adaptermicrocomputer 302 start the low output to the signal line CS whendetecting the start bit ST input from the signal line DATA. At thistime, since the camera microcomputer 205 has already started the lowoutput to the signal line CS, the signal level of the signal line CSdoes not change.

Thereafter, the camera microcomputer 205 stops the low output to thesignal line CS after the stop bit SP is output. On the other hand, afterreceiving the stop bit SP input from the signal line DATA, the lensmicrocomputer 111 and the adapter microcomputer 302 analyze the receiveddata and perform internal processing associated with the received data.When the preparation for receiving the next data is completed, the lowoutput to the signal line CS is stopped. As described above, the signallevel of the signal line CS becomes high when all of the cameramicrocomputer 205, the lens microcomputer 111, and the adaptermicrocomputer 302 stop the low output to the signal line CS. Thus, eachof the camera microcomputer 205, the lens microcomputer 111, and theadapter microcomputer 302 can confirm that the signal level of thesignal line CS becomes high after stopping the low output to the signalline CS. When each of the camera microcomputer 205, the lensmicrocomputer 111, and the adapter microcomputer 302 confirms that thesignal level of the signal line CS has become high, it can determinethat the current communication processing is completed and it is readyfor the next communication.

Next, when confirming that the signal level of the signal line CS hasreturned to the high level, the adapter microcomputer 302 starts the lowoutput to the signal line CS in order to notify the camera microcomputer205 and the lens microcomputer 111 that the broadcast communication isto be started.

Next, the adapter microcomputer 302 outputs the data to be transmitted,to the signal line DATA. The camera microcomputer 205 and the lensmicrocomputer 111 start the low output to the signal line CS whendetecting the start bit ST input from the signal line DATA. Since theadapter microcomputer 302 has already started the low output to thesignal line CS at this time, the signal level propagated to the signalline CS does not change. Thereafter, the adapter microcomputer 302 stopsthe low output to the signal line CS when it completes outputting thestop bit SR On the other hand, after receiving up to the stop bit SPinput from the signal line DATA, the camera microcomputer 205 and thelens microcomputer 111 analyze the received data and perform internalprocessing associated with the received data. Then, after thepreparation for receiving the next data is completed, the low output tothe signal line CS is stopped.

As described above, the signal transmitted through the signal line CS inthe broadcast communication serves as a signal indicating the start(execution) and the ongoing execution of the broadcast communication.

FIG. 4 illustrates an illustrative broadcast communication, but anotherbroadcast communication may be performed. For example, the datatransmitted in a single broadcast communication may be one-byte data asillustrated in FIG. 4 , but may be two-byte or three-byte data. Thebroadcast communication may be a one-way communication from the cameramicrocomputer 205 serving as a communication master to the lensmicrocomputer 111 and adapter microcomputer 302 serving as communicationslaves.

[P2P Communication]

Next follows a description of the P2P communication performed among thecamera 200 (camera microcomputer 205), the interchangeable lens 100(lens microcomputer 111), and the adapter 300 (adapter microcomputer302). The P2P communication is a one-to-one communication (individualcommunication) in which the camera 200 as the communication masterdesignates (selects) a single communication counterpart (specificaccessory apparatus) among the interchangeable lens 100 and the adapter300 as the communication slaves, and communicates data with only thedesignated communication slave. This P2P communication is also performedusing the signal line CS and the signal line DATA. A communication modein which the P2P communication is performed will be also referred to asa P2P communication mode (second communication mode).

FIG. 5 illustrates, in an example, signal waveforms of the P2Pcommunication exchanged between the camera microcomputer 205 and thelens microcomputer (specific accessory apparatus) 111 designated as thecommunication counterpart. In response to one-byte data transmissionfrom the camera microcomputer 205, the lens microcomputer 111 transmitstwo-byte data to the camera microcomputer 205. Communication modeswitching processing (between the broadcast communication mode and theP2P communication mode) and processing for designating the communicationcounterpart in the P2P communication will be described later.

Initially, the camera microcomputer 205 as the communication masteroutputs data to be transmitted to the lens microcomputer 111, to thesignal line DATA. The camera microcomputer 205 starts the low output(standby request) to the signal line CS after completing the output ofthe stop bit SP. After the camera microcomputer 205 is ready to receivethe next data, the camera microcomputer 205 stops the low output to thesignal line CS. On the other hand, after detecting the low signal inputfrom the signal line CS, the lens microcomputer 111 analyzes thereceived data input from the signal line DATA and performs internalprocessing associated with the received data. Thereafter, whenconfirming that the signal level of the signal line CS has returned tothe high level, the lens microcomputer 111 continuously outputs two-bytedata to be transmitted, to the signal line DATA.

The lens microcomputer 111 starts the low output to the signal line CSafter completing the output of the stop bit SP of the second byte.Thereafter, when becoming ready to receive the next data, the lensmicrocomputer 111 stops the low output to the signal line CS. Theadapter microcomputer 302 that is not designated as the communicationcounterpart for the P2P communication does not output the signal to thesignal line CS or the signal line DATA.

As described above, the signal transmitted through the signal line CS inthe P2P communication serves as a notification signal indicating the endof the data transmission and a standby request for the next datatransmission.

While FIG. 5 illustrates the illustrative P2P communication, another P2Pcommunication may be used. For example, data may be transmitted everyone byte at a time using the signal line DATA, or data may betransmitted every three bytes or more.

[Communication Mode Switching Processing and Communication CounterpartDesignating Processing]

Referring now to FIG. 6 , a description will be given of thecommunication mode switching processing and the communicationcounterpart designating processing in the P2P communication. FIG. 6illustrates signal waveforms during the communication mode switching andcommunication counterpart designating, which are exchanged among thecamera microcomputer 205, the lens microcomputer 111, and the adaptermicrocomputer 302. The communication counterpart of the P2Pcommunication is designated by the broadcast communication. In thisillustrative description, the adapter microcomputer 302 is designated asthe communication counterpart of the P2P communication by the cameramicrocomputer 205, and one-byte data P2P communication from the cameramicrocomputer 205 and one-byte data P2P communication from the adaptermicrocomputer 302 are executed. Thereafter, the lens microcomputer 111is designated as the communication counterpart of the P2P communicationby the camera microcomputer 205, and two-byte data P2P communicationfrom the camera microcomputer 205 and three-byte data P2P communicationfrom the lens microcomputer 111 are executed.

Initially, the camera microcomputer 205 which is the communicationmaster executes the broadcast communication according to the proceduredescribed in FIG. 4 . What is notified by this broadcast communicationis slave designation data for designating the communication counterpartwith the camera microcomputer 205 in the next P2P communication. Thelens microcomputer 111 and the adapter microcomputer 302, which are thecommunication slaves at this time, determine whether or not they aredesignated as the communication counterpart in the P2P communicationbased on the slave designation data received by the broadcastcommunication. This determination result switches the communicationmodes of the camera microcomputer 205 and the designated communicationslave (specific accessory apparatus) from the broadcast communicationmode to the P2P communication mode. Since the adapter microcomputer 302is designated herein as the communication counterpart in the next P2Pcommunication, data is transmitted and received between the cameramicrocomputer 205 and the adapter microcomputer 302 in accordance withthe procedure described in FIG. 5 . Herein, one-byte data is transmittedfrom the camera microcomputer 205 to the adapter microcomputer 302, andthen one-byte data is transmitted from the adapter microcomputer 302 tothe camera microcomputer 205.

When the P2P communication ends between the camera microcomputer 205 andthe adapter microcomputer 302, the camera microcomputer 205 can againdesignate a communication counterpart for the P2P communication by thebroadcast communication. Herein, in order to designate the lensmicrocomputer 111 as the communication counterpart for the next P2Pcommunication, the lens microcomputer 111 is set to the slavedesignation data, and the broadcast communication is executed accordingto the procedure described in FIG. 4 . In response to this broadcastcommunication, the adapter microcomputer 302 ends the P2P communication,and at the same time, the communication modes of the cameramicrocomputer 205 and the lens microcomputer 111 are switched to the P2Pcommunication mode. If no broadcast communication is executed at thisstage, the P2P communication continues between the camera microcomputer205 and the adapter microcomputer 302.

In the next P2P communication, data is transmitted and received betweenthe camera microcomputer 205 and the lens microcomputer 111 inaccordance with the procedure described in FIG. 5 . Herein, the cameramicrocomputer 205 transmits two-byte data to the lens microcomputer 111,and then the lens microcomputer 111 transmits three-byte data to thecamera microcomputer 205.

As described above, the broadcast communication can designate thecommunication counterpart for the P2P communication, and at the sametime, and the broadcast communication and the P2P communication can beswitched.

[Communication Control Processing]

A description will now be given of communication control processingperformed among the camera microcomputer 205, the lens microcomputer111, and the adapter microcomputer 302. Referring now to the flowchartin FIGS. 7A and 7B, a description will be given of processing in thebroadcast communication mode. FIG. 7A illustrates processing performedby the camera microcomputer 205, and FIG. 7B illustrates processingperformed by the lens microcomputer 111 and the adapter microcomputer302. Each of the camera microcomputer 205, the lens microcomputer 111,and the adapter microcomputer 302, each of which includes the computer,executes this processing and other processing described later inaccordance with a communication control program as a computer program.

When an event for starting the broadcast communication occurs in thestep S100, the camera microcomputer 205 turns on (connects) the groundswitch 2081 to put the signal line CS into low in the step S101.Thereby, the start of the broadcast communication is notified to thelens microcomputer 111 and the adapter microcomputer 302. The lensmicrocomputer 111 and the adapter microcomputer 302 that have detectedthe low level of the signal line CS in the step S200 permit the datareception from the signal line DATA in the step S201.

Next, the camera microcomputer 205 operates the input/output switch 2082in the step S102 to connect the signal line DATA to the data outputpart, and performs the data transmission in the step S103. Whendetecting the start bit of the signal line DATA in the step S202, thelens microcomputer 111 and the adapter microcomputer 302 turns on(connects) the lens switch 1121 and the ground switch 3031 so as toindicate the ongoing communication processing in the step S205. Thereby,the low output to the signal line CS starts. Thereafter, whendetermining that all data has been received in the step S206, the lensmicrocomputer 111 and the adapter microcomputer 302 prohibit the datareception from the signal line DATA in the step S207. Further, in thestep S208, the ground switch 1121 and the ground switch 3031 are turnedoff (disconnected) to indicate that the communication processing hasended, and the low output to the signal line CS is stopped. Herein, thenumber of bytes of data to be transmitted and received is not limited,as long as the camera microcomputer 205, the lens microcomputer 111, andthe adapter microcomputer 302 has common recognitions.

Next, in the step S104, the camera microcomputer 205 determines whetherthe data transmitted in the step S103 is a bidirectional commandincluding the transmission from the lens microcomputer 111 or theadapter microcomputer 302. If data is not the bidirectional command, thecamera microcomputer 205 turns off (disconnects) the ground switch 2081in the step S105 to stop the low output to the signal line CS, andproceeds to the step S116. If it is the bidirectional command, thecamera microcomputer 205 operates the input/output switch 2082 in thestep S106 to connect the signal line DATA to the data input part. In thestep S107, the ground switch 2081 is turned off (disconnects) to stopthe low output to the signal line CS, and it waits for the signal lineCS to become high in the step S108.

On the other hand, in the step S209, the lens microcomputer 111 and theadapter microcomputer 302 determine whether the data received in thestep S206 is the bidirectional command including the transmission fromitself. If the data is not the bidirectional command, the lensmicrocomputer 111 and the adapter microcomputer 302 proceed to the stepS215, and if the data is the bidirectional command, the lensmicrocomputer 111 and the adapter microcomputer 302 wait for the signalline CS to become high in the step S210. When the signal line CS becomeshigh, the lens microcomputer 111 and the adapter microcomputer 302notify the start of the broadcast communication by turning on(connecting) the ground switches 1121 and 3031 and by putting the signalline CS into low in the step S211. When detecting the low level of thesignal line CS in the step S109, the camera microcomputer 205 permitsthe data reception from the signal line DATA in the step S110.

Next, the lens microcomputer 111 and the adapter microcomputer 302operate the input/output switches 1122 and 3032 in the step S212 toconnect the signal line DATA to the data output part, and perform thedata transmission in the step S213. When detecting the start bit of thesignal line DATA in the step S111, the camera microcomputer 205 turns on(connects) the ground switch 2081 to indicate ongoing communicationprocessing in the step S112. Thereby, the low output to the signal lineCS starts. The lens microcomputer 111 and the adapter microcomputer 302stop the low output to the signal line CS by turning off (shut off) theground switches 1121 and 3031 in the step S214 after the transmissionsof all data are completed. If the camera microcomputer 205 determinesthat all data has been received in the step S113, it prohibits the datareception from the signal line DATA in the step S114. In the step S115,the camera microcomputer 205 turns off (disconnects) the ground switch2081 to stop the low output to the signal line CS in order to indicatethat the communication processing has ended. Herein, the number of bytesof data to be transmitted and received is not limited, as long as thecamera microcomputer 205, the lens microcomputer 111, and the adaptermicrocomputer 302 have common recognitions.

Next, the camera microcomputer 205 waits for the signal line CS tobecome high in the step S116. When the signal line CS becomes high, thecamera microcomputer 205 determines in the step S117 whether or not thelens microcomputer 111 or the adapter microcomputer 302 has beendesignated as a communication counterpart for the P2P communicationbased on the data transmitted in the step S103. If none of the lensmicrocomputer 111 and the adapter microcomputer 302 are designated asthe communication counterparts, the camera microcomputer 205 ends theprocessing as it is, and if any is designated, the camera microcomputer205 transfers to the P2P communication mode in the step S118.

On the other hand, the lens microcomputer 111 and the adaptermicrocomputer 302 stand by until the signal line CS becomes high in thestep S215. When the signal line CS becomes high, in the step S216, thelens microcomputer 111 and the adapter microcomputer 302 determinewhether or not they are designated as the communication counterpart forthe P2P communication by the camera microcomputer 205, based on the datareceived in the step S206. If none of the lens microcomputer 111 and theadapter microcomputer 302 are designated as the communicationcounterparts, the processing ends. If it is designated as thecommunication counterpart, the designated microcomputer out of the lensmicrocomputer 111 and the adapter microcomputer 302 permits the datareception from the signal line DATA in the step S217, and transfers tothe P2P communication mode in the step S218.

If the start bit is not detected in the step S202, the lensmicrocomputer 111 and the adapter microcomputer 302 confirm whether ornot the signal line CS has become high in the step S203. When the signalline CS becomes high (returns to the high level), the lens microcomputer111 and the adapter microcomputer 302 prohibit the data reception fromthe signal line DATA in the step S204 and end the processing. This isprocessing for a communication slave not designated as a communicationcounterpart for the P2P communication to respond to the low output tothe signal line CS by the P2P communication between the cameramicrocomputer 205 and another communication slave.

Referring now to flowcharts in FIGS. 8A and 8B, a description will begiven of processing in the P2P communication mode. FIG. 8A illustratesprocessing performed by the camera microcomputer 205, and FIG. 8Billustrates processing performed by a microcomputer (referred to as aspecific microcomputer hereinafter) designated as a communicationcounterpart for the P2P communication among the lens microcomputer 111and the adapter microcomputer 302.

When an event for starting the P2P communication occurs in the stepS300, the camera microcomputer 205 operates the input/output switch 2082in the step S301 to connect the signal line DATA to the data outputpart, and performs the data transmission in the step S302. Thereafter,when all data transmissions are completed, the camera microcomputer 205turns on (connects) the ground switch 2081 in the step S303 and startsthe low output to the signal line CS. On the other hand, when thespecific microcomputer detects the low level of the signal line CS inthe step S400, it determines that the data transmission from the cameramicrocomputer 205 is completed, and analyzes the data received from thesignal line DATA in the step S401.

Next, in the step S304, the camera microcomputer 205 determines whetherthe data transmitted in the step S302 is the bidirectional commandincluding the transmission from the specific microcomputer. If it is notthe bidirectional command, the camera microcomputer 205 turns off(disconnects) the ground switch 2081 in the step S305 to stop the lowoutput to the signal line CS. In the step S306, it waits for the signalline CS to become high before proceeding to the step S311. If the datais the bidirectional command, the camera microcomputer 205 operates theinput/output switch 2082 in the step S307 to connect the signal lineDATA to the data input part. In the step S308, the ground switch 2081 isturned off (disconnected) to stop the low output to the signal line CS.

On the other hand, after waiting for the low level of the signal line CSin the step S402, the specific microcomputer determines in the step S403whether the data received in the step S401 is the bidirectional commandincluding the transmission from itself. If it is not the bidirectionalcommand, the specific microcomputer turns on (connects) and turns off(disconnects) the ground switch (1121 or 3031) in the steps S404 andS405. Thereby, the low output to the signal line CS is started andstopped, and the flow proceeds to the step S411. In the bidirectionalcommand, the specific microcomputer operates the input/output switch(1122 or 3032) in the step S406 to connect the signal line DATA to thedata output part, and performs the data transmission in the step S407.Thereafter, when all data transmissions are completed, the specificmicrocomputer starts the low output to the signal line CS by turning on(connecting) the ground switch (1121 or 3031) in the step S408.

Next, when detecting the low level in the signal line CS in the stepS609, the camera microcomputer 205 determines in the step S310 that thedata transmission from the specific microcomputer has been completed,and analyzes the data received from the signal line DATA. On the otherhand, in the step S409, the specific microcomputer operates theinput/output switch (1122 or 3032) to connect the signal line DATA tothe data input part. Thereafter, the specific microcomputer turns off(disconnects) the ground switch (1121 or 3031) in the step S410 to stopthe low output to the signal line CS.

Next, the camera microcomputer 205 waits for the signal line CS tobecome high in the step S311. Thereafter, when an event for starting thebroadcast communication occurs in the step S312, the cameramicrocomputer 205 transfers to the broadcast communication mode in thestep S313. On the other hand, the specific microcomputer waits for thesignal line CS to become high in the step S411 and ends the processing.

Thus, this embodiment properly switches the meaning (function) of thesignal transmitted through the signal line CS between the broadcastcommunication and the P2P communication. Thereby, the cameramicrocomputer 205, the lens microcomputer 111, and the adaptermicrocomputer 302 can communicate with one another with the small numberof signal lines (or channels).

[Authentication Communication Processing]

Referring now to FIGS. 9 and 10 , a description will be given ofauthentication communication processing according to this embodiment.FIG. 9 illustrates signal waveforms in the authentication communicationprocessing performed among the camera microcomputer 205, the lensmicrocomputer 111, and the adapter microcomputer 302.

The top of the figure illustrates data communicated by the signal lineDATA, “Camera” indicates data output by the camera microcomputer 205,“Adapter” indicates data output by the adapter microcomputer 302, and“Lens” indicates data output from the microcomputer 111. “CS signal(camera)” indicates a signal output state (referred to as a CS signalstate hereinafter) of the signal line CS detected by the cameramicrocomputer 205, and “CS output (camera)” indicates a signal outputfrom the camera microcomputer 205 to the signal line CS. “CS signal(adapter)” indicates a CS signal state detected by the adaptermicrocomputer 302, and “CS output (adapter)” indicates a signal outputfrom the adapter microcomputer 302 to the signal line CS. “CSSW”indicates the state of the CS switch 3033 controlled by the adaptermicrocomputer 302, and Low indicates the connection state. “CS signal(lens)” indicates a CS signal state detected by the lens microcomputer111, and “CS output (lens)” indicates a signal output from the lensmicrocomputer 111 to the signal line CS.

A flowchart in FIG. 10 illustrates a flow of authenticationcommunication processing. This authentication communication processingis performed when the power supply starts from the camera 200 to theinterchangeable lens 100 and the adapter 300 after the camera 200detects the connection of the interchangeable lens 100 through thedetection switch (1123) provided in the camera 200. At the start of theauthentication communication processing, the camera microcomputer 205transmits an authentication start request command via the signal lineDATA by the broadcast communication in the step S500. In other words,the authentication start communication is performed. This processing isperformed as a preprocess for the authentication communication by thecamera microcomputer 205. At this time, the CS switch 3033 is set to theconnected state. The processing in the broadcast communication and P2Pcommunication performed later is as described with reference to FIGS.7A, 7B, 8A, and 8B. As described above, the adapter microcomputer 302and the lens microcomputer 111 output different signals (low and high)to the signal line CS between the ongoing communication with the cameramicrocomputer 205 (from a communication start to an end) and thecommunication standby in the broadcast communication and the P2Pcommunication.

The adapter microcomputer 302 and the lens microcomputer 111 that havereceived the authentication start request command perform receptionprocessing in the broadcast communication in the steps S506 and S513,respectively. If the received result is an authentication start requestcommand, the adapter microcomputer 302 switches the CS switch 3033 to adisconnected state in the step S507. Here, the timing of this switchingis after the adapter microcomputer 302 stops the low output to thesignal line CS (after the step S208 in FIG. 7 ), but may be just beforeor simultaneous with stopping the low output.

Next, the camera microcomputer 205 sends an authentication requestcommand via the communication line DATA in the step S501 when theadapter microcomputer 302 stops the low output to the signal line CS andthe communication circuit is waiting for the communication. In otherwords, the authentication request communication is performed. In thesubsequent processing, the camera microcomputer 205 performs theauthentication communication. The authentication request command isslave designation data for designating as a designated slave (specificaccessory apparatus) the communication slave that has received itthrough the broadcast communication. Since the communication line CS isdisconnected by the CS switch 3033 in the step S507, the low output tothe communication line CS in the step S501 is not detected by the lensmicrocomputer 111. On the other hand, since the communication line DATAis connected, the authentication request command has been transmitted tothe lens microcomputer 111. However, the authentication request commandis a command premised on the broadcast communication in which data canbe received only when the communication line CS is low. Hence, the lensmicrocomputer 111 that has received the authentication request commandwhile the communication line CS is high ignores this command.

On the other hand, the adapter microcomputer 302 receives theauthentication request command via the communication line DATA by thebroadcast communication in the step S508. Since the adaptermicrocomputer 302 that has received the authentication request commandhas received the authentication request command for the first time, itis the slave designation data transmitted to itself, and determines thatthe next P2P communication is communication addressed to itself.

Next, in the step S502, the camera microcomputer 205 transmits an IDcommunication request command via the communication line DATA by the P2Pcommunication. In other words, the authentication informationcommunication is performed. At this time, the camera microcomputer 205does not recognize that the communication counterpart of the P2Pcommunication is the adapter microcomputer 302. This is because it isnot yet known at this point how many accessories are connected to thecamera 200. The camera microcomputer 205 only knows that any of theconnected communication slaves responds to the P2P communication bydesignating the designated slave by the authentication request commandtransmitted in the step S501.

In the step S509, the adapter microcomputer 302 designated as thedesignated slave receives the ID communication request command by theP2P communication, and in response, sends its own ID information(authentication information) to the camera microcomputer 205 via thesignal line DATA by the P2P communication. Thereafter, the adaptermicrocomputer 302 switches the CS switch 3033 to the connected state inthe step S510. Herein, the switching timing is after the adaptermicrocomputer 302 stops the low output to the signal line CS (after thestep S410 in FIG. 8 ), but it may be just before or simultaneous withthe stop of the low output.

The P2P communication in the steps S502 and S509 may be performed onlyin one reciprocation between the camera microcomputer 205 and theadapter microcomputer 302 as illustrated in FIG. 9 or may be performedin two or more reciprocations.

Furthermore, although the timing for switching the CS switch 3033 to theconnected state is after the step S509 in this flowchart, it may bebefore the step 509 (after the reception of the authentication requestcommand in the step S508). This is because the adapter microcomputer 302that has received the authentication request command by the broadcastcommunication recognizes that it is the slave designation data toitself, and the lens microcomputer 111 that has not received theauthentication request command does not recognize that it is the slavedesignation data to itself. Hence, even when the CS switch 3033 isswitched to the connected state after the step S508, only the adaptermicrocomputer 302 responds to the ID communication request command inthe step S509.

Next, when the adapter microcomputer 302 stops the low output to thesignal line CS and the communication circuit is waiting for thecommunication, the camera microcomputer 205 resends the authenticationrequest command via the communication line DATA by the broadcastcommunication in the step S503. Herein, since the communication line CSis connected, the adapter microcomputer 302 receives the authenticationrequest command in the step S511, and the lens microcomputer 111 alsoreceives it in the step S514. However, the adapter microcomputer 302 hasalready finished the communication (or the authentication) in responseto the authentication request command and the ID communication requestcommand, and thus ignores the authentication request command at thisstage. On the other hand, this is the first reception of theauthentication request command for the lens microcomputer 111, the lensmicrocomputer 111 interprets it as the slave designation data to itselfand prepares for the P2P communication.

Thereafter, the camera microcomputer 205 transmits the ID communicationrequest command via the communication line DATA by the P2P communicationin the step S504. Herein, the camera microcomputer 205 does notrecognize that the counterpart of the P2P communication is the lensmicrocomputer 111. This is because of the same reason as that for theadapter microcomputer 302. In the step S515, the lens microcomputer 111transmits its ID information (authentication information) to the cameramicrocomputer 205 via the signal line DATA by the P2P communication inresponse to the ID communication request command. When confirming thatthe received ID information is that of the interchangeable lens 100, thecamera microcomputer 205 determines that no further communication slaveto be authenticated is connected. Then, in the step S505, the cameramicrocomputer 205 transmits the authentication end request command forending the authentication communication processing via the signal lineDATA by the broadcast communication. In other words, the authenticationend communication is performed. In the steps S512 and 516, the adaptermicrocomputer 302 and the lens microcomputer 111 receive anauthentication end request command. Thereby, the authenticationcommunication processing ends.

Thus, in this embodiment, the camera microcomputer 205 sequentiallydesignates the designated slave using the broadcast communicationwhenever the CS output state indicates the ongoing standby of thecommunication, and performs the authentication communication using thebroadcast communication and the P2P communication.

Variation

ID information as the authentication information transmitted from theadapter microcomputer 302 and the lens microcomputer 111 to the cameramicrocomputer 205 in response to the ID communication request commandmay include information of a serial number for each type of accessoryapparatus (such as 00 for the interchangeable lens and 01 for theextender). Moreover, the ID information may include information to whichthe meaning was allocated for every bit. It may contain information of aplurality of bytes. The ID information may be information indicating thetype and function of the accessory apparatus.

The above authentication communication processing has described that thecamera microcomputer 205 confirms that the ID information belongs to theinterchangeable lens 100 and determines the end of the authenticationcommunication. Alternatively, the ID information may include informationindicating the interchangeable lens and information for instructing theend of the authentication communication, and the camera microcomputer205 may detect it and determine the end of the authenticationcommunication. In addition to the ID information communication, aconfirmation communication for asking the communication slave aboutwhether or not the authentication communication can be terminated may beseparately performed by the P2P communication before and after the IDcommunication.

This embodiment has described the single adapter 300 connected betweenthe camera 200 and the interchangeable lens 100, but allows a pluralityof adapters connected in series. Even when a plurality of adapters areconnected, it is possible to authenticate each adapter and theinterchangeable lens 100 in a short time in the same procedure asdescribed above. At this time, the plurality of adapters thatsimultaneously receive the authentication start request command by thebroadcast communication almost simultaneously set the CS switch to thedisconnected state, so that the subsequent authentication is alwaysperformed sequentially from the adapter closer to the camera 200 one byone. Similar to the case where one adapter is connected, theinterchangeable lens 100 is finally authenticated, and a series ofauthentication communication processing is completed.

When the adapter 300 is not connected and the interchangeable lens 100is directly connected to the camera 200, the authenticationcommunication is performed for the interchangeable lens 100 withoutperforming part of the authentication communication for the adapter 300in the authentication communication processing illustrated in FIGS. 9and 10 .

The adapter 300 in this embodiment may be an extender as describedabove, an adapter including a drivable optical element (such as a focuslens, a diaphragm, and an image stabilization lens), or an adapterincluding a variety of sensors (a phase difference sensor, an angularvelocity). The above variation is similarly applied to the followingsecond embodiment.

This embodiment can sequentially perform an authentication communicationin order from an accessory apparatus closer to the camera 200 byswitching the CS switch 3033 provided in the adapter 300 in a camerasystem that performs a communication using two lines (two channels) orthe signal line CS and the signal line DATA. Finally, the authenticationcommunication of the interchangeable lens can be performed. Thereby,even if a plurality of accessory apparatuses are connected to the camera200, the authentication communication can be performed in a short time.

Second Embodiment

Next follows a description of a second embodiment according to thepresent invention. The first embodiment has discussed the communicationline CS connected and disconnected by the CS switch 3033, whereas thisembodiment connects and disconnects the communication line DATA by theswitch. Since the configuration of the camera system in this embodimentis similar to that of the first embodiment (FIG. 1 ), a descriptionthereof will be omitted.

FIG. 11 illustrates communication circuits provided among the cameramicrocomputer 205, the adapter microcomputer 302, and the lensmicrocomputer 111. This embodiment is different from the firstembodiment (FIG. 2 ) in that the first embodiment includes the CS switch3033 for connecting and disconnecting the communication line CS whereasthis communication circuit provides a data switch (channel switch) 3034for connecting and disconnecting the communication line DATA in theadapter 300′.

The adapter microcomputer 302′ can connect and disconnect the signalline DATA by switching the DATA switch 3034 between the connected stateand the disconnected state. In the disconnected state of the DATA switch3034, the data output state from the camera side (camera 200 in thisembodiment) of the adapter 300′ to the signal line DATA is nottransmitted to the interchangeable lens side (interchangeable lens 100in this embodiment). The data output state from the adapter 300′ to thesignal line DATA is not transmitted to the interchangeable lens side. Inother words, the data communication using the signal line DATA isunavailable to the communication slave on the interchangeable lens sideof the adapter 300′.

Referring now to FIGS. 12 and 13 , a description will be given ofauthentication communication processing according to this embodiment.FIG. 12 illustrates signal waveforms in the authentication communicationprocessing performed among the camera microcomputer 205, the lensmicrocomputer 111, and the adapter microcomputer 302. The signal outputstate (CS signal state) of the signal line CS is shown at the top in thefigure. The lower “DATA (camera)” indicates data output from the cameramicrocomputer 205 to the signal line DATA, and “DATA (adapter)”indicates data output from the adapter microcomputer 302 to the signalline DATA. “DATA (lens)” indicates data output from the lensmicrocomputer 111 to the signal line DATA. “CS output (camera)”indicates a signal output from the camera microcomputer 205 to thesignal line CS, and “CS output (adapter)” indicates a signal output fromthe adapter microcomputer 302 to the signal line CS. “CS output (lens)”indicates a signal output from the lens microcomputer 205 to the signalline CS. “DATASW” indicates the state of the DATA switch 3034 controlledby the adapter microcomputer 302, and Low indicates the connectionstate.

A flowchart in FIG. 13 illustrates a flow of authenticationcommunication processing. This authentication communication processingis started when the power supply starts from the camera 200 to theinterchangeable lens 100 and the adapter 300′ after the camera 200detects the connection of the interchangeable lens 100 through thedetection switch (not shown) provided in the camera 200.

At the start of the authentication communication processing, the cameramicrocomputer 205 transmits an authentication start request command viathe signal line DATA by the broadcast communication in the step S600. Inother words, the authentication start communication is performed. Thisprocessing is performed as a preprocess for the authenticationcommunication by the camera microcomputer 205. At this time, the DATAswitch 3034 is set to the connected state. The processing in thebroadcast communication and the P2P communication performed later is asdescribed with reference to FIGS. 7A, 7B, 8A, and 8B. Even in thisembodiment, the adapter microcomputer 302 and the lens microcomputer 111output different signals (low and high) to the signal line CS betweenthe communication with the camera microcomputer 205 (from acommunication start to an end) and the ongoing standby of thecommunication in the broadcast communication and the P2P communication.

The adapter microcomputer 302 and the lens microcomputer 111 that havereceived the authentication start request command perform the broadcastcommunication reception processing in the steps S606 and S613,respectively. If the received result is an authentication start requestcommand, the adapter microcomputer 302 switches the DATA switch 3034 toa disconnected state in the step S607. Herein, the timing of thisswitching is after the adapter microcomputer 302 stops the low output tothe signal line CS (after step S208 in FIG. 7 ), but may be just beforeor simultaneous with stopping of the low output.

Next, the camera microcomputer 205 sends the authentication requestcommand via the communication line DATA by the broadcast communicationin the step S601 when the adapter microcomputer 302 stops the low outputto the signal line CS and the communication circuit is waiting for thecommunication. In other words, the authentication request communicationis performed. In the subsequent processing, the camera microcomputer 205performs the authentication communication. The authentication requestcommand includes slave designation data for designating as thedesignated slave (specific accessory apparatus) the communication slavethat has received it through the broadcast communication similar to thefirst embodiment. Since the communication line DATA is disconnected bythe DATA switch 3034 in the step S607, the lens microcomputer 111 doesnot detect the authentication request command via the communication lineDATA in the step S601. On the other hand, since the communication lineCS is connected, the lens microcomputer 111 detects that thecommunication line CS becomes low and then becomes high. However, thelens microcomputer 111 ends the processing by considering that there wasno communication since no data is sent via the communication line DATA.

On the other hand, the adapter microcomputer 302 receives theauthentication request command through the broadcast communication inthe step S608. The adapter microcomputer 302 that has received theauthentication request command has received the authentication requestcommand for the first time, and thus interprets that it is the slavedesignation data transmitted to itself and the next P2P communication iscommunication addressed to itself.

Next, in the step S602, the camera microcomputer 205 transmits an IDcommunication request command via the signal line DATA by the P2Pcommunication. In other words, the authentication informationcommunication is performed. At this time, the camera microcomputer 205does not recognize that the communication counterpart of the P2Pcommunication is the adapter microcomputer 302. This is because it isnot yet known at this point how many accessories are connected to thecamera 200. The camera microcomputer 205 only knows that one of theconnected communication slaves responds to the P2P communication bydesignating the designated slave by the authentication request commandtransmitted in the step S601.

In the step S609, the adapter microcomputer 302 designated as thedesignated slave receives the ID communication request command by theP2P communication, and in response, transmits the ID information(authentication information) to the camera microcomputer 205 via thesignal line DATA by the P2P communication. Thereafter, the adaptermicrocomputer 302 switches the DATA connection switch 3034 to theconnected state in the step S610. Herein, the switching timing is afterthe adapter microcomputer 302 stops the low output to the signal line CS(after the step S410 in FIG. 8 ), but it may be just before orsimultaneous with stopping of the low output.

The P2P communication in the steps S602 and S609 may be performed onlyin one reciprocation between the camera microcomputer 205 and theadapter microcomputer 302 as illustrated in FIG. 12 , or may beperformed in two or more reciprocations.

While the timing for switching the DATA switch 3034 to the connectedstate is after the step S609 in this flowchart, it may be before thestep 609 (after the reception of the authentication request command inthe step S608). This is because the adapter microcomputer 302 that hasreceived the authentication request command by the broadcastcommunication recognizes that it is the slave designation data toitself, and the lens microcomputer 111 that has not received theauthentication request command does not recognize that it is the slavedesignation data to itself. Hence, even if the DATA switch 3034 isswitched to the connected state after the step S608, only the adaptermicrocomputer 302 responds to the ID communication request command inthe step S609.

Next, when the adapter microcomputer 302 stops the low output to thesignal line CS and the communication circuit is waiting for thecommunication, the camera microcomputer 205 resends the authenticationvia the signal line DATA by the broadcast communication in the stepS603. Herein, since the communication line DATA is connected, theadapter microcomputer 302 receives the authentication request command inthe step S611, and the lens microcomputer 111 also receives it in thestep S614. However, the adapter microcomputer 302 has once finished thecommunication (or authentication) in response to the authenticationrequest command and the ID communication request command, and thusignores the authentication request command at this time. On the otherhand, since this is the first reception of the authentication requestcommand for the lens microcomputer 111, the lens microcomputer 111interprets it as slave designation data for itself and prepares for theP2P communication.

Thereafter, the camera microcomputer 205 transmits an ID communicationrequest command via the signal line DATA by the P2P communication in thestep S604. Herein, the camera microcomputer 205 does not recognize thatthe counterpart of the P2P communication is the lens microcomputer 111.This is because of the same reason as that for the adapter microcomputer302. In the step S615, the lens microcomputer 111 transmits its IDinformation (authentication information) to the camera microcomputer 205via the signal line DATA by the P2P communication in response to the IDcommunication request command. When the camera microcomputer 205confirms that the received ID information is that of the interchangeablelens 100, the camera microcomputer 205 determines that no furthercommunication slave to be authenticated is connected. In the step S605,the camera microcomputer 205 transmits an authentication end requestcommand for ending the authentication communication processing via thesignal line DATA by the broadcast communication. In other words, theauthentication end communication is performed. In the steps S612 and616, the adapter microcomputer 302 and the lens microcomputer 111receive the authentication end request command. As a result, theauthentication communication processing ends.

Thus, even in this embodiment, the camera microcomputer 205 sequentiallydesignates the designated slave using the broadcast communicationwhenever the CS output state indicates the ongoing standby of thecommunication, and performs the authentication communication using thebroadcast communication and the P2P communication.

This embodiment sequentially performs the authentication communicationin order from an accessory apparatus closer to the camera 200 byswitching the DATA switch 3034 provided in the adapter 300′ in a camerasystem that performs the communication using two lines (two channels) orthe signal line CS and the signal line DATA. Finally, the authenticationcommunication of the interchangeable lens can be performed. Thereby,even if a plurality of accessory apparatuses are connected to the camera200, the authentication communication can be performed in a short time.

The embodiment described above can be used in combination with anothercommunication channel in addition to the communication channel includingthe notification channel CS and the data communication channel DATA.

An example thereof will be described with reference to FIG. 14 . In FIG.14 , those elements which are corresponding elements in FIG. 1 will bedesignated by the same reference numerals, and a duplicate descriptionthereof will be omitted. Moreover, FIG. 14 omits an illustration of partof components described in FIG. 1 . The notification channel CS and thedata communication channel DATA described above are communication linesfor a communication called a third communication. In the thirdcommunication, when the operation member 304 is operated by the user,the adapter microcomputer 302 and the camera microcomputer 205communicate the fact of the operation and the operational amount betweenthem. Even when the operation member 130 is operated by the user, thecommunication may be performed between the lens microcomputer 111 andthe camera microcomputer 205 using the third communication line.

The lens microcomputer 111 controls the communicator 131 for the firstcommunication and the communicator 132 for the second communication, inaddition to the communicator 112. In addition to the communicator 112,the camera microcomputer 205 controls the communicator 209 for the firstcommunication and the communicator 210 for the second communication.

A description will now be given of the first communication. The firstcommunication is a communication performed via the communicators 131 and209. The communicator 131 following an instruction from the lensmicrocomputer 111 and the communicator 209 following an instruction fromthe camera microcomputer 205 communicate with each other via anotification channel CS1, a data communication channel DCL, and a datacommunication channel DLC. The communicators 131 and 209 set the voltagelevel of the notification channel CS1, the communication rate (dataamount per unit time) and communication voltage in the asynchronouscommunication. In response to an instruction from the lens microcomputer111 or the camera microcomputer 205, data is transmitted and receivedvia the data communication channel DCL and the data communicationchannel DLC.

The notification channel CS1 is a signal line used to notify acommunication request from the camera 200 to the interchangeable lens100 or the like. The data communication channel DCL is a channel usedwhen data is transmitted from the camera 200 to the interchangeable lens100, and the data communication channel DLC is a channel used when datais transmitted from the interchangeable lens 100 to the camera 200.

In the first communication, the camera microcomputer 205 and the lensmicrocomputer 111 communicate with each other by a clock synchronouscommunication or asynchronous communication. An initial communicationperformed when the interchangeable lens 100 is connected to the camera200 is also made initially by the first communication. The cameramicrocomputer 205 and the lens microcomputer 111 communicateidentification information of the interchangeable lens 100, and when itis determined that the interchangeable lens 100 mounted on the camera200 is compatible with the asynchronous communication, the communicationmethod is changed from the clock synchronization communication to theasynchronous communication. As a result of the communication of theidentification information, the camera microcomputer 205 may identifywhether or not the interchangeable lens 100 is compatible with the thirdcommunication that performs the communication including the adapter 300.When determining that the interchangeable lens 100 is compatible withthe third communication, the camera microcomputer 205 may perform theauthentication communication for recognizing the interchangeable lens100 and the intermediate adapter 300 via the P2P communication.

Next follows a description of the second communication. The secondcommunication is a one-way communication from the interchangeable lens100 to the camera 200. The second communication is performed via thecommunicators 132 and 210. The communicator 132 following an instructionfrom the lens microcomputer 111 and the communicator 210 following aninstruction from the camera microcomputer 205 communicate with eachother via a notification channel CS2 and a data communication channelDLC2. The camera communicator 208 and the lens communicator 118 transmitand receive data by the clock synchronous communication or asynchronouscommunication. By using the data communication channel DLC2 of thesecond communication channel together with the data communicationchannel DLC of the first communication, it becomes possible to transmita large amount of data from the interchangeable lens 100 to the camera200 in a short time.

Other Embodiments

Embodiment(s) of the present invention can also be realized by acomputer of a system or apparatus that reads out and executes computerexecutable instructions (e.g., one or more programs) recorded on astorage medium (which may also be referred to more fully as a‘non-transitory computer-readable storage medium’) to perform thefunctions of one or more of the above-described embodiment(s) and/orthat includes one or more circuits (e.g., application specificintegrated circuit (ASIC)) for performing the functions of one or moreof the above-described embodiment(s), and by a method performed by thecomputer of the system or apparatus by, for example, reading out andexecuting the computer executable instructions from the storage mediumto perform the functions of one or more of the above-describedembodiment(s) and/or controlling the one or more circuits to perform thefunctions of one or more of the above-described embodiment(s). Thecomputer may comprise one or more processors (e.g., central processingunit (CPU), micro processing unit (MPU)) and may include a network ofseparate computers or separate processors to read out and execute thecomputer executable instructions. The computer executable instructionsmay be provided to the computer, for example, from a network or thestorage medium. The storage medium may include, for example, one or moreof a hard disk, a random-access memory (RAM), a read only memory (ROM),a storage of distributed computing systems, an optical disk (such as acompact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™),a flash memory device, a memory card, and the like.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

The present invention can provide a camera to which a plurality ofaccessory apparatuses are connected, which can perform an authenticationcommunication with all the accessory apparatuses in a short time.

What is claimed is:
 1. A camera on which an accessory apparatus ismountable, the camera comprising a camera controller configured tocontrol a communication with the accessory apparatus using a signaltransmission channel used for a signal transmission between the cameraand the accessory apparatus, and a data communication channel used for adata communication between the camera and the accessory apparatus,wherein using the data communication channel, the camera controller isconfigured to provide a first communication that is a data communicationwithout a designation of a communication counterpart and a secondcommunication that is a data communication with a designatedcommunication counterpart, and wherein whenever detecting a signalindicating an ongoing standby of the first communication output to thesignal transmission channel from one accessory apparatus that is notauthenticated by the camera, the camera controller authenticates the oneaccessory apparatus by performing an authentication communication withthe one accessory apparatus.
 2. The camera according to claim 1, whereinthe camera controller performs the authentication communication afternotifying a start of the authentication communication using the firstcommunication.
 3. The camera according to claim 1, wherein the cameracontroller performs the authentication communication using the firstcommunication and the second communication.
 4. The camera according toclaim 3, wherein the authentication communication includes: acommunication that requests a transmission of authentication informationof the one accessory apparatus using the first communication; and acommunication that receives the authentication information from the oneaccessory apparatus using the second communication.
 5. The cameraaccording to claim 1, wherein the one accessory apparatus include aninterchangeable lens apparatus or adapter apparatus connected betweenand the interchangeable lens apparatus and the camera, and wherein thecamera controller performs the authentication communication in orderfrom the adapter apparatus connected nearest to the camera to theinterchangeable lens apparatus among the at least one adapter apparatus.6. The camera according to claim 5, wherein the camera controllerperforms an authentication end communication to notify an end of theauthentication communication using the first communication when theauthentication communication for the interchangeable lens apparatusends.
 7. The camera according to claim 5, wherein using the firstcommunication and the second communication, the camera controllercontrols the adapter apparatus including a channel switch configured toconnect and disconnect the signal transmission channel, so as to set thechannel switch to a disconnected state in the authenticationcommunication for the adapter apparatus, and to set the channel switchto a connected state after the authentication communication iscompleted.
 8. The camera according to claim 5, wherein using the firstcommunication and the second communication, the camera controllercontrols the adapter apparatus including a channel switch configured toconnect and disconnect the data communication channel, so as to set thechannel switch to a disconnected state in the authenticationcommunication for the adapter apparatus, and to set the channel switchto a connected state after the authentication communication iscompleted.
 9. The camera according to claim 5, wherein the cameraincludes a detection switch configured to detect a connection of theinterchangeable lens apparatus, and wherein the camera controllerperforms the authentication communication when detecting the connectionof the interchangeable lens apparatus through the detection switch. 10.An accessory apparatus connectable to a camera, the accessory apparatuscomprising an accessory controller configured to control a communicationwith the camera using a signal transmission channel used for a signaltransmission between the camera and the accessory apparatus, and a datacommunication channel used for a data communication between the cameraand the accessory apparatus, and wherein the accessory controller isconfigured to provide a first communication that is a data communicationwithout a designation of a communication counterpart and a secondcommunication that is a data communication with a designatedcommunication counterpart, outputs a signal indicating the accessorycontroller is waiting for the first communication to the signaltransmission channel when the accessory controller is not authenticatedby the camera, and performs an authentication communication for causingthe camera that has detected the output to authenticate the accessoryapparatus.
 11. The accessory apparatus according to claim 10, whereinthe authentication communication includes: a communication that requiresauthentication information of the accessory apparatus to be transmittedfrom the camera using the first communication; a communication thattransmits the authentication information to the camera in response to arequest for the authentication information using the secondcommunication.
 12. The accessory apparatus according to claim 10,wherein the accessory controller receives data indicating an end of theauthentication communication output from the camera when theauthentication communication ends for an interchangeable lens apparatus.13. The accessory apparatus according to claim 10, wherein the accessoryapparatus is an interchangeable lens apparatus, or an adapter apparatusconnected between the interchangeable lens apparatus and the camera. 14.The accessory apparatus according to claim 13, further comprising achannel switch configured to connect and disconnect the signaltransmission channel, wherein in response to the first communication orthe second communication from the camera, the accessory controller setsthe channel switch to a disconnected state while the authenticationcommunication for the adapter apparatus is performed, and sets thechannel switch to a connected state after the authenticationcommunication is completed.
 15. The accessory apparatus according toclaim 13, further comprising a channel switch configured to connect anddisconnect the data communication channel, wherein in response to thefirst communication or the second communication from the camera, theaccessory controller sets the channel switch to a disconnected statewhile the authentication communication for the adapter apparatus isperformed, and sets the channel switch to a connected state after theauthentication communication is completed.
 16. A communication controlmethod for a camera on which an accessory apparatus is mountable, andconnected to a signal transmission channel used to a signal transmissionbetween the camera and the accessory apparatus, and a data communicationchannel used for a data communication between the camera and theaccessory apparatus, the camera being configured to provide, using thedata communication channel, a first communication that is a datacommunication without a designation of a communication counterpart and asecond communication that is a data communication with a designatedcommunication counterpart, the communication control method comprisingthe steps of: causing the camera to detect a signal indicating anongoing standby of the first communication output to the signaltransmission channel from one accessory apparatus that is notauthenticated by the camera; and causing the camera to perform anauthentication communication with the one accessory apparatus, whereinwhenever detecting the signal indicating the ongoing standby, the cameraauthenticates the one accessory apparatus by performing theauthentication communication with the one accessory apparatus.
 17. Acommunication control method for an accessory apparatus connectable to acamera, the accessory apparatus being connected to a signal transmissionchannel used for a signal transmission between the camera and theaccessory apparatus, and a data communication channel used for a datacommunication between the camera and the accessory apparatus, theaccessory apparatus being configured to provide, using the datacommunication channel, a first communication that is a datacommunication without a designation of a communication counterpart and asecond communication that is a data communication with a designatedcommunication counterpart, the communication control method comprisingthe steps of: causing the accessory apparatus to output a signalindicating the accessory controller is waiting for the firstcommunication to the signal transmission channel when the accessorycontroller is not authenticated by the camera, and causing the accessoryapparatus to perform an authentication communication for causing thecamera that has detected the output to authenticate the accessoryapparatus.
 18. A non-transitory computer-readable storage medium storinga communication control program that is a computer program that causes acomputer in a camera on which an accessory apparatus is mountable toexecute processing, the camera connected to a signal transmissionchannel used for a signal transmission between the camera and theaccessory apparatus, and a data communication channel used for a datacommunication between the camera and the accessory apparatus, whereinusing the data communication channel, the camera is configured toprovide a first communication that is a data communication without adesignation of a communication counterpart and a second communicationthat is a data communication with a designated communicationcounterpart, wherein the processing comprising the steps of: causing thecamera to detect a signal indicating an ongoing standby of the firstcommunication output to the signal transmission channel from oneaccessory apparatus that is not authenticated by the camera; and causingthe camera to perform an authentication communication with the oneaccessory apparatus, wherein whenever detecting the signal indicatingthe ongoing standby, the camera authenticates of the one accessoryapparatus by performing the authentication communication with the oneaccessory apparatus.
 19. A non-transitory computer-readable storagemedium storing a communication control program that is a computerprogram that causes a computer in an accessory apparatus connectable toa camera to execute processing, the accessory apparatus being connectedto a signal transmission channel used for a signal transmission betweenthe camera and the accessory apparatus, and a data communication channelused for a data communication between the camera and the accessoryapparatus, and the accessory apparatus being configured to provide afirst communication that is a data communication without a designationof a communication counterpart and a second communication that is a datacommunication with a designated communication counterpart, theprocessing comprising the steps of: causing the accessory apparatus tooutput a signal indicating the accessory controller is waiting for thefirst communication to the signal transmission channel when theaccessory controller is not authenticated by the camera, and causing theaccessory apparatus to perform an authentication communication forcausing the camera that has detected the output to authenticate theaccessory apparatus.
 20. An accessory apparatus connectable to a camera,the accessory apparatus comprising an accessory controller configured tocontrol a communication with the camera using a signal transmissionchannel used for a signal transmission between the camera and theaccessory apparatus, and a data communication channel used for a datacommunication between the camera and the accessory apparatus, andwherein the accessory controller is configured to provide a firstcommunication in which a voltage level of the signal transmissionchannel while receiving data from the camera is a first level and asecond communication in which a voltage level of the signal transmissionchannel while receiving data from the camera is a second level higherthan the first level, outputs a signal indicating the accessorycontroller is waiting for the first communication to the signaltransmission channel when the accessory controller is not authenticatedby the camera, and performs an authentication communication for causingthe camera that has detected the output to authenticate the accessoryapparatus.
 21. The accessory apparatus according to claim 20, whereinthe authentication communication includes: a communication that requiresauthentication information of the accessory apparatus to be transmittedfrom the camera using the first communication; a communication thattransmits the authentication information to the camera in response to arequest for the authentication information using the secondcommunication.
 22. The accessory apparatus according to claim 20,wherein the accessory controller receives data indicating an end of theauthentication communication output from the camera when theauthentication communication ends for an interchangeable lens apparatus.23. The accessory apparatus according to claim 20, wherein the accessoryapparatus is an interchangeable lens apparatus, or an adapter apparatusconnected between the interchangeable lens apparatus and the camera. 24.The accessory apparatus according to claim 23, further comprising achannel switch configured to connect and disconnect the signaltransmission channel, wherein in response to the first communication orthe second communication from the camera, the accessory controller setsthe channel switch to a disconnected state while the authenticationcommunication for the adapter apparatus is performed, and sets thechannel switch to a connected state after the authenticationcommunication is completed.
 25. The accessory apparatus according toclaim 23, further comprising a channel switch configured to connect anddisconnect the data communication channel, wherein in response to thefirst communication or the second communication from the camera, theaccessory controller sets the channel switch to a disconnected statewhile the authentication communication for the adapter apparatus isperformed, and sets the channel switch to a connected state after theauthentication communication is completed.